Around 70 percent of HIV-infected people smoke tobacco. Antretroviral therapy (ART) has been effective in enhancing immune systems in HIV infected people. However, the full extent of improvements vary, making clarifying the effects of smoking difficult.

Previous studies have shown that HIV infection and smoking influences T cell activation. T cells are a type of white blood cell that has a central role in the bodies’ immunity. The further effects on other associated immune defects, such as immune activation (IA) or microbial translocation (MT) is not understood in the context of HIV infection.

Now a team from the University of Miami in the U.S. has conducted the first comprehensive analysis of the combined effect of HIV infection, and smoking, on the immune system of HIV infected smokers on ART.

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Four groups of participants were used for the study: 25 HIV infected smokers and 25 HIV infected non-smokers, 15 uninfected smokers and 15 uninfected non-smokers as a control. HIV infected participants were on combination ART and were virologically suppressed. Study methods included questionnaires on drug, tobacco and alcohol, use, past and present history, physical, and laboratory testing.

Compared to non-smokers, smokers of HIV infected and uninfected groups showed significantly higher specific T cells known as CD4+ and CD 8+, or so called “helper” T cell. With a higher magnitude in HIV infected smokers.

The study also looked at microbial translocation; one of the most important factors implicated in triggering IA in infected people, and is associated with the severity of HIV infection.

Compared to HIV infected non-smokers, MT was higher in smokers of both groups and correlated directly with T cell activation. Markers for immune exhaustion were also significantly higher in smokers.
The overall results suggest that smoking in HIV infected people leads to increased immune activation (IA), Microbial translocation (MT) and impairment of T cell functions that eventually may influence disease progression and management.

“HIV infection results in chronic IA and overall immunological dysfunction, both of these closely associate with progression to AIDS” say the authors.

Even in HIV infected people who are successfully treated with Highly Active Antiretroviral Therapy (HAART), persistent immune activation is linked with increased death rates.

The study also confirmed that specific T-cell functional capacity was reduced in smokers regardless of their HIV status. This is in agreement with previous studies reporting protein and gene changes involved in immunity are altered in smokers.

This leaves HIV infected smokers at increased risk of bronchitis and bacterial pneumonia due to higher immune defects say the authors.

“Smoking is widespread among HIV infected people, studies are needed to further evaluate the cumulative effect of smoking on impairment of the immune system and accelerated disease progression.”